Mortality and psychiatric morbidity among drug addicts in Stockholm

• Aim: The aim of the thesis was to assess overall mortality and cause-specific mortality among drug addicts in Stockholm and also to study the relationship between cannabis and psychiatric morbidity and mortality. Methods: All studies are based on the Stockholm County inpatient register. Follow-up of mortality during the periods 1973-84, 1971-81, 1980-90, 1971-95 were performed through record linkage with the National Cause of Death register. Information on cause-specific mortality was obtained from autopsy protocols. Information on cannabis use and psychiatric morbidity was obtained through medical records. Results: Follow-up of overall and cause-specific mortality: For all causes of death the drug addicts showed an excess mortality compared with the general population. The excess mortality in causes of death related to alcoholism and drug dependence was 43 times that of the general population. For suicides and undetermined causes of death the mortality was 18 times higher than that of the general population. A comparison of the cause-specific mortality in two cohorts of drug addicts selected 1971-72 and 1980-81 showed a significant increase in cause of death diagnoses of drug dependence in the latter cohort (RR-4.2, CI 2.6-6.7). The mortality varied by type of substance abuse; opiate addicts had the highest excess mortality compared with the general population; in the 1971-72 cohort the SMR was 15 and in the 1980-81 cohort it was 22. A two-fold increased risk of early mortality was found for the opiate addicts in the two cohorts compared with the central stimulant addicts. The most common cause of death among the patients was accidents, followed by suicides. Many of the deaths occurred within a week of hospital discharge. Cannabis and schizophrenia: Of 229 selected cannabis dependent patients, 112 were classified as having schizophrenia and 117 had other psychiatric disorders. Regular cannabis use preceded or occurred in the same year as the onset of psychotic symptoms for a majority of the schizophrenics. The results support the notion that cannabis is a risk factor for schizophrenia. Mortality, cannabis use and psychosis: For two groups of patients, one comorbid group with a diagnoses of cannabis use and psychosis and one psychosis group, the mortality rates were significantly higher compared with the general population. Unnatural causes of death dominated and a majority were suicides. The toxic effect of cannabis in itself did not seem to affect mortality among males. The results for females indicated a higher mortality rate, possibly due to a more severe psychological and/or psychiatric background in comorbid females rather than an effect of cannabis use per se. Conclusion: The results show a significantly increased mortality for drug addicts compared with the general population, with accidents and suicides as the dominant causes of death. The highest risk for death was found in males, opiate addicts and persons over 35 years. The association between cannabis and psychiatric illness is complex, but analyses based on patient data, combined with scrutiny of medical records, are valuable tools for further research in this area. Better care and treatment of high risk persons could prevent at least some of the accidental deaths and suicides.

Nyckelord

Mortality, cause-specific mortality, follow-up, drug addiction,comorbidity, cannabis, schizophrenia.

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